This invention relates to a novel process for preparing spirobiindanols. The process employs an alkylaryl bisphenol in the presence of a dry heterogeneous acid catalyst in toluene at reflux.
The use of mineral acids, such as 18 percent aqueous HBr, concentrated aqueous H.sub.2 SO.sub.4 (U.S. Pat. No. 3,271,463), Lewis acids such as BF.sub.3, and p-toluenesulfonic acid as catalysts for the conversion of bisphenols to spirobiindanols is well known. These procedures, however, require costly catalyst removal steps, such as washing and neutralization, in the purification of the final product because the catalyst is dissolved in the reaction mixture or is present in a second phase. Furthermore, the crude products obtained by these methods are very difficult to purify due to the presence of many by-products. Spirobiindanols are also available from phenol and acetone via the bisphenol derivative.
The process of the present invention provides a cleaner crude product under milder conditions with an easier and less costly catalyst removal step. The catalyst allows for faster conversion and can also be easily recycled. In summary, the advantages of this process over the known methods are: (1) the reaction is faster; (2) the reaction conditions are milder as far as temperature and corrosiveness; (3) the catalyst can be removed more easily; (4) the catalyst can be easily recycled; (5) higher yields; and (6) the crude product is cleaner and more easily purified.
Spirobiindanols impart high rigidity, lipophilicity, and oxidative and thermal stability to polymer systems such as epoxies, polyesters, and polycarbonates. Spirobiindanols are also applicable in membranes for gas separation. Spirobiindanols can also be reacted with halohydrins to form diglycidyl ethers and diglycidyl ethers to form polyhydroxy ethers which are useful in thermoforming processes, for the manufacture of articles such as combs and high temperature structural parts, and for use as adhesives.